Allegro MicroSystems A3966SLB-T

Overview

A3966SLB-T from Allegro MicroSystems is a dual full-bridge PWM motor driver IC designed to control both windings of a two-phase bipolar stepper motor. It delivers ±650 mA continuous output current per bridge, supports up to 30 V load supply voltage, and integrates fixed-frequency PWM current regulation with user-selectable blanking via external RC timing network. It is used in precision motion control systems such as industrial automation actuators and medical lab equipment positioning stages.

For engineers reviewing the A3966SLB-T datasheet, A3966SLB-T pinout, A3966SLB-T application, or A3966SLB-T equivalent, key selection criteria include its Satlington® sink drivers, internal thermal shutdown with 15 °C hysteresis, ±750 mA peak current capability, and 16-pin SOICW package with fused ground pins for enhanced thermal dissipation.

Technical Context

The A3966SLB-T implements two independent full-bridge outputs with separate PHASE and ENABLE inputs per channel, enabling bidirectional current control and fast decay modes. Its internal PWM current-control circuit uses a fixed-frequency oscillator (22.9–27.9 kHz with 56 kΩ/680 pF) and blanking window (1.3 µs typical) to suppress false triggering during switching transients.

Each bridge features crossover-current protection, UVLO (4.1–4.6 V enable threshold), and integrated ground-clamp/flyback diodes. The Satlington® sink structure achieves 0.3–0.7 V saturation at +400/+650 mA, while source drivers exhibit 1.7–2.1 V saturation at –400/–650 mA, minimizing conduction losses under load.

Key Specifications

Pinout & Package

Package: 16-pin SOICW (suffix LB), with pins 4 and 13 internally fused to the die pad for low-thermal-resistance grounding. No electrical isolation required for these pins.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual full-bridge motor driver applications.

Compared with TB6600HG and DRV8825, the A3966SLB-T offers superior thermal management via fused ground pins, lower conduction loss through Satlington® sinks, and user-tunable blanking-making it optimal for compact, thermally constrained bipolar stepper systems operating at ≤650 mA.

Availability

A3966SLB-T is available at Aetrix Electronics and suitable for industrial CNC positioning stages, medical fluid dispensing pumps, and automated test equipment handlers requiring stable component supply and long-term lifecycle continuity.

Supply support for A3966SLB-T includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Allegro MicroSystems is a U.S.-based designer of high-performance magnetic sensing and power IC solutions, headquartered in Manchester, NH.

The A3966 product line delivers integrated stepper motor drivers with emphasis on thermal robustness, current accuracy, and protection integration for industrial motion control applications.

FAQ

What is the maximum continuous output current supported by the A3966SLB-T?

The A3966SLB-T supports ±650 mA continuous output current per full-bridge channel under specified thermal conditions (TA = 25 °C, proper PCB heatsinking). Peak current capability is ±750 mA, but sustained operation above 650 mA requires verification of junction temperature limits and derating per ambient conditions and duty cycle. The A3966SLB-T datasheet specifies 1.87 W package power dissipation at 25 °C ambient.

How does the A3966SLB-T implement current regulation without external op-amps or DACs?

The A3966SLB-T uses an internal fixed-frequency PWM current-control circuit that compares sensed voltage across an external resistor (RS) to a threshold derived from VREF divided by 4. When current reaches ITRIP = VREF/(4 × RS) + 18 mA, the source driver turns off. The A3966SLB-T's oscillator and blanking logic then manage recirculation and re-enable timing autonomously-eliminating need for external regulation circuitry.

Can the A3966SLB-T be used with 3.3 V logic controllers?

No-the A3966SLB-T requires VCC between 4.75 V and 5.5 V for proper logic operation, and its digital inputs (PHASE/ENABLE) have VIH minimum of 2.4 V and VIL maximum of 0.8 V. Direct interfacing with 3.3 V microcontrollers requires level-shifting circuitry; the A3966SLB-T is not 3.3 V tolerant and may malfunction or damage inputs if driven outside its specified logic voltage range.

What is the purpose of pins 4 and 13 on the A3966SLB-T SOICW package?

Pins 4 and 13 on the A3966SLB-T are internally fused to the die pad and serve as dedicated low-thermal-resistance ground connections. They are electrically grounded and require no isolation-instead, they must be soldered to a large copper pour to maximize heat transfer from the silicon die. This design enables the A3966SLB-T to achieve 1.87 W power dissipation at 25 °C ambient, significantly improving reliability over standard SOIC packages.

Does the A3966SLB-T support microstepping or only full-step operation?

The A3966SLB-T supports only full-step and half-step excitation modes via its PHASE/ENABLE interface-it does not include built-in microstepping logic or current interpolation circuitry. Microstepping requires external controller-generated PWM signals applied to ENABLE pins or external current DACs. The A3966SLB-T provides precise, protected full-bridge drive for each winding, making it suitable as the power stage in custom microstepping designs where timing and current profiling are handled upstream.